1. Field of Invention
The present invention relates to a dental impression tray, and more particularly to a dental impression tray that allows an operator to take an impression of a patient's dentition and simultaneously align the impression with the patient's face. This facilitates the fabrication of symmetrical, facially well-aligned, and aesthetic crowns, porcelain veneers, and/or bridges by the dental laboratory technician.
2. Description of the Related Art
When a patient requires a crown for at least one tooth, a dentist has to take an impression of the patient's dentition to produce a crown therefrom. When a patient requires a single incisor crown, the dental technician can produce the crown according to the other incisor. However, when two or more front teeth are involved, the dentist is required to not only take an impression of these teeth, but also align them with the patient's face using a device called Facial Plane Relator or FPR for short. The reason for this additional step of using the FPR is to ensure that the crowns fabricated by the dental technician are not slanted relative to the patient's face.
With reference to FIGS. 7A and 7B, FIG. 7A shows a conventional dental impression tray and FIG. 7B shows a conventional FPR (40).
With further reference to FIG. 8, a conventional impression tray comprises a base (30). The base (30) is curved corresponding to a human dentition and has an outer wall (31), an inner wall (33), a membrane (32) and a handle (34). The membrane (32) is formed between the outer wall (31) and the inner wall (33), is made up of meshes and is able to hold impression material such as silicon rubber or the like. The handle (34) is formed on the outer wall (31) opposite to the inner wall (33) to allow a dentist to hold the impression tray.
With further reference to FIGS. 9 and 10, the FPR (40) comprises an arch (44), a horizontal bar (42) and a vertical bar (41). Using the pupils of the eyes (50) as a guide, the horizontal bar (42) corresponds to a horizontal facial midline (91). Using the bridge of the nose (49B) and the philtrum (49A) as guides, the vertical bar (41) corresponds to a vertical facial midline (92). The arch (44) has an outer edge and an inner edge. The inner edge has multiple protrusions (45). The protrusions (45) radially protrude from the inner edge of the arch (44) and are arranged on the inner edge at intervals, the purpose of which is to help hold the impression material onto the arch (44). The horizontal bar (42) is formed tangentially on the outer edge of the arch (44) and has a clamp (43). The vertical bar (41) is secured by the clamp (43) of the horizontal bar (42) and holds the vertical bar (41) perpendicular to the horizontal bar (42).
When the conventional dental impression tray is used, a patient bites into the membrane (32) holding the impression material. After the impression materials have cured, the dental impression tray (30) is removed from a patent's mouth and a dental impression is obtained. The next step is to use the FPR (40) for determining the patient's dental-facial alignment. The protrusions (45) are applied with liberal amounts of impression materials for the patient to bite. When the patient bites the FPR (40) just medial (48) to the protrusions (45), the vertical and the horizontal bars (41, 42) are adjusted to align respectively with the bridge of the nose (49B), the philtrum (49A), and the eyes (50), so that the vertical bar (41) is in parallel with the bridge of the nose (49B) as well as the philtrum (49A) and the horizontal bar (42) is in parallel with the eyes (50). After the impression material has cured, the FPR (40) is detached from the mouth to obtain the relationship between the patient's dentition and face. The dental laboratory technician then uses this completed FPR (40) to fabricate crowns or dental veneers to ensure that the patient does not end up with a crooked smile after the crowns or veneers are cemented in the patient's mouth.
The entire process involved the dentist having to take two separate and distinct steps in order to obtain the impression and the relation and the patient is required to bite the impression materials twice. Therefore, obtaining the impression and the relation doubles both the dentist and the patient's time and cost as well as raising the discomfort level of the patient.
With reference to FIG. 11, an another FPR comprises a bitten sheet (51), an outer wall (52), a connecting bar (53), a horizontal bar (54) and a vertical bar (55). The bitten sheet (51) holds impression material and allows a patient to bite into the impression material. The outer wall (52) is formed on a side of the bitten sheet (51). An end of the connecting bar (53) is formed integrally on and protrudes from the outer wall (52). A central part of the horizontal bar (54) integrally connects perpendicularly with another end of the connecting bar (53) to align with patient's face horizontally. An end of the vertical bar (55) connects integrally with and protrudes upward from the central part of the horizontal bar (54) and is perpendicular to the horizontal bar (54) and the connecting bar (53) to align with patient's nose.
However, all elements of the another FPR are formed integrally, so the horizontal bar (54) and the vertical bar (55) both cannot be adjust. Therefore, the horizontal bar (54) and the vertical bar (55) cannot obtain an accurate relationship between the patient's dentition and face.
The present invention combines the function of an impression tray with a FPR such that only one step is required in obtaining both.